An explosion of communication and information technologies including internet based systems has motivated a world wide effort to implement optical communication networks to take advantage of a large bandwidth available with optical communication. The capacity of optical fiber technology can be expanded further with the interfacing of optical fibers with planar optical structures. With increasing demands, more channels are needed to fulfill the system functions. Integrated planar components can be used to replace discrete optical components to supply the desired capacity. To form these integrated structures, there is considerable interest in the formation of specific compositions applied to substrates such that the compositions provide appropriate optical properties. In order to form optical devices with high quality optical coatings from these materials, the coating properties need to be specified accordingly.
Basic characteristics of optical materials comprise surface quality, uniformity and optical quality. Optical quality refers to small enough absorption and scattering loss to achieve desired levels of transmission. Optical quality also comprises the uniformity of optical properties, such as index-of-refraction, and bi-refringence properties. In addition, optical quality is affected by interface quality, such as the interface between the core layers and cladding layers. For silica (SiO2) and several other materials, preferred forms for optical transmission are a glass, while for some other materials single crystal or polycrystalline forms may have the highest quality optical transmission.